Do vegans typically rely on assumptions for this?

Yeah I guess so. A food being vegan just basically means theres no meat, dairy or eggs in it. So I don’t know if its an assumption necessarily to take it for granted that rice or whatever is vegan, you just kind of know that there’s no meat, dairy or eggs in there (unless its deep fried, which can complicate things, so you might need to ask the waiter/waitress).